Method of forming shells or molded parts



Nov. 9, 1965 D. A. BRAFFORD METHOD OF FORMING SHELLS 0R MOLDED PARTS Filed May 9, 1962 d m 2 m W 5 M g a M hw United States Patent 3,216,889 METHOD OF FORMING SHELLS 0R MOLDED PARTS Donald A. Brafford, Beloit, Wis., assignor to Beloit Corporation, Beloit, Wis., a corporation of Wisconsin Filed May 9, 1962, Ser. No. 193,455 1 Claim. (Cl. 162-218) The present invention relates to an improved apparatus .and method for forming shells or hollow forms from a liquid suspension of fibers.

More particularly, the invention pertains to forcing a fluid stock having a suspension of particles or fibers through the porous wall of a mold to deposit the fibers on a forming surface to directly form an article or shell of a desired shape. The apparatus and method are particularly well adapted to the formation of hollow tubular shaped thin Walled shells which are uniform in thickness and have an accurate outer dimension and are strong. While the method and apparatus of the present invention form a complete article, in some instances it may be desirable to further treat the article such as by impregnating the formed shell with an impregnate binder, sizing it to accurate shape and size and subjecting it to a controlled drying and curing operation and trimming the edges of the shell.

The mechanism and apparatus of the present invention overcome ditficulties inherent in the formation of a thin walled shell and provide improvements in mechanisms and methods heretofore available. In the formation of such a shell it is important that uniform shell thickness be obtained and that a uniform layer of fibers or particles be deposited on the forming surface of the mold. The uniformity of distribution of particles on the mold surface, the proper distribution, and the control of the quantity of distribution are important to the formation of a strong shell wall of uniform thickness.

It is accordingly an object of the present invention to provide an improved method and mechanism for the formation of a shell on a forming surface of a porous mold, which will obtain a better control of the quantity of material deposited on the inner surface of the mold and Will obtain a uniform deposit to obtain a shell of uniform wall thickness.

A further object of the invention is to provide a method and mechanism for pulp molding using a female mold operating on a full flow filter principle wherein the mold element operates in a semi-closed system and uniform flow resistance is obtained during a forming cycle so that stock containing particles in suspension will deposit the particles uniformly over the entire mold area and uniform flow resistance will exist.

A still further object of the invention is to provide a molding system of the type described wherein improved general control is obtained to adjust pressures and flow rates.

Another object of the invention is to provide a method and apparatus of a type described wherein the pressure differential across the mold is controllable so that the differential may be reduced to permit the use of higher delivery pressures without exceeding the physical limits of the mold Wall.

Other objects, advantages and features will become more apparent with the teaching of the principles of the invention in connection with the disclosure of the preferred embodiment thereof in the specification, claim and drawings, in which:

The figure of the drawing is a somewhat schematic illustration of a mechanism constructed in accordance with the principles of the present invention and adapted to operate in accordance with the method of the invention.

As shown on the drawing:

3,216,889 Patented Nov. 9, 1965 Fee A porous mold 10 formed of a material such as ceramic is shown as being formed in generally-cylindrical shape with an inner forming surface 11. The forming surface 11 may be altered somewhat from its cylindrical shape to obtain a shell of the shape desired, and generally the wall of the mold 10 is of uniform thickness to offer uniform flow resistance to fluid flowing therethrough. The cylindrical mold defines therein a distribution chamber 12 to which stock is delivered. A pressure differential exists across the wall of the mold 111 due to forcing the stock into the distribution chamber 12 so that the fluid will flow outwardly through the wall of the mold 10 and the particles or fibers in suspension within the stock will be deposited on the forming surface 11.

The mold wall 10 may be formed of a material such as individual glass beads coated with an epoxy resin to bind the beads together into the mold shape. A description of a preferred form of mold material and the method of making such material is provided in the copending patent application of Modersohn and Hornbostel, entitled Mold, U.S. Serial No. 89,451, filed February 15, 1961, now abandoned.

The fluid stock which is supplied to the interior mold may be of the general nature of stock used in the formation of paper. More particularly, the stock is preferably water with particles or fibers in suspension at a consistency of 0.01% to 2.0%, and a preferred consistency of 0.05% is employed. Particles or fibers suitable for the formation of the desired shell are in suspension in the water, and a preferred arrangement employs a kraft pulp comprising kraft fibers and cotton linters. This obtains a strong shell wall and provides features well suited for the mechanism and process to be described. The stock may also contain additional material such as a compatible resinous impregnate and/ or binder, e.g. urea-formaldehyde or melamine-formaldehyde resins, cellulose esters and ethers, polyvinyl alcohols, etc.

Outside of the mold 10 is an outer or collection chamber 13 which receives the white water after it has flowed through the mold 10, and this chamber is defined by an outer housing or casing 14 which supports the mold. The casing is shown as extending across the bottom of the mold, and the top of the mold is closed by a cover 15, which may be opened to a raised position 15' for access to the interior of the mold for cleaning, and for removing the shell after it has been formed. It will be appreciated by those versed in the art that various arrangements for removing the mold, or for removing the shell from the mold may be employed.

Within the inner or the distribution chamber 12 within the mold is a stock distributor 16 which supplies the fluid stock to the forming surface 11 in an evenly distributed pattern of flow. For this purpose, the stock is delivered by a supply line 17. The distributor 16 is provided wtih a plurality of stock conducting branches each of which has outlet openings or nozzles which are at the tips of the schematically illustrated branches and which are substantially uniformly spaced with respect to each other, and are uniformly spaced inwardly from the forming wall so that each portion of surface area of a forming wall will receive an equal supply of stock. This will aid in the uniform distribution of fibers on the forming surface 11.

The stock is received by the supply line 17 from a supply tank 18 which is provided with a measured quantity of stock. The supply tank 18 is filled with the measured quantity, and the fluid stock is then continually recirculated through the mold until substantially all the fibers are deposited on the forming surface 11. This obtains a good control of the wall thickness inasmuch as the stock consistency is known and the quantity of stock is known so that the amount of fibers deposited upon the forming surface 11 will be accurately predetermined.

The stock is forced into the mold at a pressure by a pump 19 in the supply conduit '17. The pressure pump 19 may be adapted to deliver stock to the mold at a relatively high pressure, but the pressure differential across the forming surface 11 and through the mold is controlled in order to permit higher pump pressures as may result when the stock begins to build up on the forming surface 11 without exceeding the physical limits of the mold wall 10.

Also within the supply line is a shut-off valve Q, downstream of the pump 19.

For filling the supply tank 18, a filler line 23 leads into the top of the tank, and the quantity is measured by a float control 21 which is electrically connected to a filling valve T in the line 23 to shut off the valve when a predetermined level of stock is obtained in the supply tank 18.

During a forming cycle, the white water from the collection chamber 13 around the mold is returned to the supply tank through a return line 20 and admixes with the stock in the tank 18 to be recirculated.

'The stock is agitated by an agitator 24 to maintain the particles in suspension, and the agitator is driven in rotation by a motor 25.

A pressure relief by-pass line 26 is connected to the supply line 17 downstream of the pressure pump 19 and returns fluid to the supply tank 18 when a valve S opens. The valve is operated by a pressure control 27 which is set to open the valve at a maximum predetermined pressure. The valve S is a safety valve and opens in case safe operating pressure is exceeded to return stock to the supply tank.

For draining the supply tank a drain line 28 is connected thereto controlled by a drain valve R.

For draining the collection chamber 13 at the end of an operation, a drain line 29 is connected thereto con trolled by a drain valve P. In the drain line 29 is a vacuum pump 30 which forcibly draws the liquid from the entire casing 14 through the walls of the mold.

A feature of the invention is the provision of a flow restricting valve in the discharge line 20 leading from the collection chamber 13 to the tank 18. The restricting valve 0 controls the release of White Water from the collection chamber 13 and thereby controls the pressure differential across the mold 10. A shut-off valve N is also positioned in the return line 20 upstream of the variable control valve 0. For operation the O valve is set at an opening which will obtain the proper pressure differential in accordance with other factors including the delivery output pressure of the pump 19.

In beginning the cycle of operations, the mold casing v14 is closed by placing the cover in the closed position, and valves P, Q and R are closed. The valve 0 is preset for the desired flow rate, and valve N is open.

The supply tank 18 is filled from the feed line 23 until the float control 21 shuts off the valve T. The agitator 24 is then started.

The valve Q is then opened and the pump 19 is started which fills the inner distributor chamber 12 with stock. The outer collection chamber 13 will fill with white Water as the liquid flows through the mold 1t and the white water containing the fines will be returned to the supply tank 18, and operation is continued until the shell is formed on the forming surface 11 and all the fibers in the stock are collected.

At the end of the forming cycle, the pump 19 is stopped and the drain valve R is opened. The drain valve P is opened and the shut-off valve N is closed and the cover 15 is raised. The vacuum pump 30 is started to drain the housing 14. The system can then be re-operated for the next cycle and the cycle is repeated for production of shells.

Thus it will be seen that I have provided an improved method and apparatus for molding shells and articles of accurate and uniform size and Wall thickness, which meets the objectives and advantages above set forth.

The drawings and specification present a detailed disclosure of the preferred embodiments of the invention, and it is to be understood that the invention is not limited to the specific forms disclosed, but covers all modifications, changes and alternative constructions and methods falling within the scope of the principles taught by the invention.

I claim as my invention:

A method of forming hollow shells with a porous shaped mold having a forming surface comprising,

measuring a predetermined quantity of fluid stock having particles in suspension, forcing said stock through the mold in a flow to deposit the particles 'on the forming surface, and continuing to recirculate the fluid received from the mold admixing it with the stock until substantially all of the particles in the stock have been deposited.

References Cited by the Examiner UNITED STATES PATENTS 464,218 12/91 Johns et al. 162-384 1,267,632 5/18 Claussen 162-219 1,536,566 5/25 Cooper 162-228 1,551,257 8/25 Little 162-228 1,618,146 2/27 Buel 162-408 1,962,656 6/34 Hall 162-218 2,131,813 10/38 Ma'rguerat et al. 162-410 2,841,054 7/58 Muller et al. 162-387 FOREIGN PATENTS 322,575 7/20 Germany.

DONALL H. SYLVESTER, Primary Examiner. MORRIS O. WOLK, Examiner. 

